Two Britons and two Irish men and a woman have been arrested after a half tonne haul of cannabis was seized from a yacht off Spain.

The arrests were made as part of joint operation involving Irish drugs squad officers, customs and the Spanish police and navy.

The yacht Colin Hannah was boarded on Thursday afternoon and the drugs haul, believed to have originated in North Africa, was seized.

The two Britons were detained on the yacht. The Irish people were arrested in follow-up raids on the Spanish mainland.

The drugs are worth at least three million euro (£2.4 million) on the street and had been destined for the Irish market, customs officers said.

All those arrested are aged between 40 and 60.

The 34ft boat had been based in Cork.

In a statement Ireland's Revenue customs division said that Operation Ciana/Fortuna was intelligence-led and supported by Spanish authorities.

"As a result of an intelligence-led drug trafficking investigation (Operation Ciana/Fortuna) into the importation and distribution of illicit drugs into the (Irish) State by sea, Revenue, the Garda National Drugs Unit and the Spanish National Police targeted a Cork-based organised crime gang," it said.

The boat was intercepted and boarded yesterday afternoon by the Spanish navy.

Investigations are ongoing both nationally and internationally, Irish authorities said.